Girls, she notices what I wear?

So I work with a girl and a lot of the time I wear the same kind of clothes but occasionally I willwear a new jumper or smarter jeans (if i am going out after work) I notice when this happens, she glances at me a good few times. Like I had a different top on and I could see her looking at me and glancing.
Why would she appear to be so bothered?
Girls, she notices what I wear?
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